However, Change et al (2018) reported that ROS‐independent ER stress promoted the stemness properties of cancer‐initiating cells.38 In the present study, CoPP treatment did not elevate the intracellular peroxide production via flow cytometric analysis using DCHFDA as a fluorescent dye, and addition of NAC showed no inhibition on CoPP‐induced HO‐1 and apoptosis in human colorectal carcinoma cells. The gene discussed is HMOX1; the disease is cancer.